Tom Browder:
# added alias IPv4s:
up ip addr add 142.54.186.3/29 dev $IFACE label $IFACE:0
down ip addr del 142.54.186.3/29 dev $IFACE label $IFACE:0
Ironically, the "modern tools" aspect is the thing that you are
in fact aiming to eliminate here. /etc/network/interfaces
is best treated as an entirely descriptive mechanism, with as
little imperative stuff in it as can be arranged. Here, you are
getting rid of the imperative explicit invocations of the ip
command, the "modern tool" as you mention, and replacing them with
the descriptive "stanzas" that /etc/network/interfaces
already has as a mechanism for non-imperatively describing
multiple IPv4/IPv6 addresses on a single eth0
interface.
ifup and ifdown are best thought of as
translators, as their manual page implies. They take what is in /etc/network/interfaces
and translate it into the necessary sequences of imperative
commands for actually doing the job, which they run under the
covers. Those underlying commands can include bootpc,
avahi-autoipd, settle-dad.sh, pon,
poff, wvdial, dhclient, dhclient3,
pump, udhcpc, dhcpd, kill,
ip, and (sic!) ifconfig, all invoked
with various parameters calculated from the /etc/network/interfaces
description.
They aren't the only translators for that file. For example,
here's what happens when one runs your proposed non-imperative /etc/network/interfaces
(with the typing errors mentioned elsewhere cleaned up) through
mine, which translates
from that description into (roughly) the rc.conf
configuration format for FreeBSD/TrueOS:
JdeBP % sudo redo -C /etc/system-control/convert/ rc.conf
Password:
redo: INFO: rc.conf: Redone.
JdeBP % sed -ne '/etc.network.interfaces/,/sysrc:/p' /etc/system-control/convert/rc.conf
# Converted from /etc/network/interfaces:
network_interfaces="lo eth0 "
ifconfig_lo="AUTO inet 127.0.0.1 "
ifconfig_eth0="AUTO inet 142.54.186.2 netmask 255.255.255.248 gateway 142.54.186.1 "
ifconfig_eth0_ipv6="inet6 2604:4300:a:95::2 netmask ffff:ffff:ffff:ffff:: "
ifconfig_eth0_aliases="inet 142.54.186.3
inet 142.54.186.4
inet 142.54.186.5
inet 142.54.186.6
inet6 2604:4300:a:95::3
inet6 2604:4300:a:95::4
inet6 2604:4300:a:95::5
inet6 2604:4300:a:95::6"
# dump by sysrc:
JdeBP %